title: Sonographic prediction of vaginal delivery in prolonged labor: a two-center study.
abstract: OBJECTIVE
  To investigate whether head-perineum distance (HPD) measured by transperineal ultrasound is predictive of vaginal delivery and time remaining in labor in nulliparous women with prolonged first stage of labor and to compare the predictive value with that of angle of progression (AoP).
  
  
  METHODS
  This was a prospective observational study at Stavanger University Hospital, Norway and Addenbrooke's Hospital, Cambridge, UK from January 2012 to April 2013, of nulliparous women with singleton pregnancies with cephalic presentation at term with prolonged first stage of labor. We used transperineal ultrasound to measure HPD (shortest distance between the outer bony limit of the fetal skull and the perineum) and AoP (angle between a line through the long axis of the symphysis and the tangent to the fetal head) and transabdominal ultrasound to classify fetal head position. The main outcomes were vaginal delivery and time remaining in labor.
  
  
  RESULTS
  Of 150 women enrolled, 39 underwent delivery by Cesarean section. The area under the receiver-operating characteristics curve for the prediction of vaginal delivery was 81% (95% CI, 73-89%) using HPD as the test variable and 72% (95% CI, 63-82%) using AoP. HPD was ≤ 40 mm in 84 (56%) women, of whom 77 (92%; 95% CI, 84-96%) delivered vaginally. HPD was > 40 mm in the other 66 (44%) women, of whom 34 (52%; 95% CI, 40-63%) delivered vaginally. AoP was ≥ 110° in 84 of the 145 (58%) in whom this was available and, of these, 74 (88%; 95% CI, 79-93%) delivered vaginally. AoP was < 110° in the other 61 (42%) women, of whom 35 (57%; 95% CI, 45-69%) delivered vaginally. Multivariable logistic regression analysis showed that HPD ≤ 40 mm (odds ratio (OR), 4.92; 95% CI, 1.54-15.80), AoP ≥ 110° (OR, 3.11; 95% CI, 1.01-9.56), non-occiput posterior position (OR, 3.36; 95% CI, 1.24-9.12) and spontaneous onset of labor (OR, 4.44; 95% CI, 1.42-13.89) were independent predictors for vaginal delivery. Both ultrasound methods were predictive for the time remaining in labor.
  
  
  CONCLUSIONS
  Transperineal ultrasound measurement of HPD and AoP provide important information about the likelihood of vaginal delivery and the time remaining in labor in nulliparous women with prolonged labor.
authors.affiliation: Department of Obstetrics and Gynecology, Stavanger University Hospital, Stavanger, Norway; National Center for Fetal Medicine, Trondheim University Hospital (St Olavs Hospital), Trondheim, Norway.
authors.forename: T M
authors.initials: TM
authors.lastname: Eggebø
authors.forename: W A
authors.initials: WA
authors.lastname: Hassan
authors.forename: K Å
authors.initials: KÅ
authors.lastname: Salvesen
authors.forename: E
authors.initials: E
authors.lastname: Lindtjørn
authors.forename: C C
authors.initials: CC
authors.lastname: Lees
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D007746:Labor Presentation; D007747:Labor Stage, First / Q000502:physiology*; D010502:Perineum / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011379:Prognosis; D011446:Prospective Studies; D013997:Time Factors; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055815:Young Adult
keywords: Cesarean section; angle of progression; head-perineum distance; occiput posterior position